Time flies by quick. I am already in my 6th week of the internship, and I feel like it just started yesterday. In this blog post, I will talk about my project and what I have done so far.
A Glimpse of Project
I am working with libcamera, which is an open-source camera stack and framework for Linux, Android, and ChromeOS. My project revolves around working on both the kernel side, VIMC driver, and the libcamera. The ultimate goal of the internship is to make VIMC support multistreaming, as well as to give multistreaming support to libcamera’s VIMC pipeline handler.
The Report
For the past five weeks, I have been trying to understand VIMC through several small issues, such as adding support for formats with an alpha component in them, writing text over tpg generated test-image, adding control for the same, etc.
I have also worked on libcamera issues. I have changed libcamera::V4L2PixelFormat::toString() to return a FourCC instead of hex digits, libcamera::V4L2SubdeviceFormat::toString() to return a MBUS name instead of its predefined values, and libcamera::PixelFormat::toString() to return libcamera::formats defined names for the DRM formats instead of their hexadecimal digits. libcamera::PixelFormat::toString() prints libcamera defined names instead of the FourCCs and modifiers of the DRMs because using drm_fourcc.h in libcamera created a dependency on this header that is packaged differently between distributions, so instead of using drm_fourcc.h, libcamera had to define constants for the libcamera supported pixel formats in a new file, formats.h. While trying to print the FourCCs and modifiers for the DRMs we also realised that though DRM fourccs look like they have a per-plane modifier, they are, in fact, all the same. Hence I also changed the passing of a set to define a PixelFormat, to a single value. It took me a lot of time to set up environment for developing libcamera on the latest media-master, since I don’t have a spare hardware for the same. So, currently I am using Virtme and I have mentioned the steps to set it up in previous blog post.
During this time, I also learnt about configfs, which is a filesystem-based manager of kernel objects. Configfs is meant to be mounted on /config, and like sysfs, it uses directories as the way of representing objects. I understoofd this so as to understand how VIMC can use configfs instead of hardcoded configuration through this patchset by Dafna. In the coming weeks, I will work on bringing multistream support in VIMC.
